The ATP-binding cassette (ABC) transporters, also called the "traffic ATPases", comprise a superfamily of membrane proteins that mediate transport and channel functions in prokaryotes and eukaryotes (Higgins, C. F. (1992) Annu. Rev. Cell Biol. 8:67-113). ABC proteins share a similar overall structure and significant sequence homology. All ABC proteins contain a conserved domain of approximately two hundred amino acid residues which includes one or more nucleotide binding domains. A majority of these proteins are involved in active transport of molecules across membranes. Eukaryotic ABC proteins include: P-glycoproteins, also known as multidrug resistance (MDR) proteins, which are associated with resistance to a wide range of hydrophobic drugs (MDR1; Gottesman, M. M. & Pastan, I. (1993) Annu. Rev. Biochem. 62:385-427) or with phosphatidylcholine transport (MDR2; Ruetz, S. & Gros, P. (1994) Cell 77:1071-1081); CFTR, the cystic fibrosis transmembrane conductance regulator (Welsh, M. J. & Smith, A. E. (1993) Cell 73:1251-1254); TAP proteins, the transporters associated with antigen processing in mammalian cells (Androlewicz, M. J. et al. (1994) Proc. Natl. Acad. Sci. USA 91:12716-12720); cMOAT/cMRP1, which is associated with transport of glutathione, glucuronide, and sulfate conjugates across the canalicular membrane (Buchler, M. et al. (1996) J. Biol. Chem. 271:15091-15098); and STE6, which exports the a-factor mating pheromone of S. cerevisiae (Michaelis, S. (1993) Semin. Cell Biol. 4:17-27). Prokaryotic ABC proteins include periplasmic nutrient permeases, such as those responsible for uptake of maltose (MalFGK) and histidine (HisMPQ) in gram-negative bacteria, and toxin exporters such as those required for export of hemolysin (HlyB) and colicin (ColV) from E. coli (Higgins, supra).
Savary, S. et al. (1997; Genomics 41:275-275) recently identified a novel ABC transporter, denoted ABC7, in mouse. The predicted 629 amino acid mouse ABC7 translation product contains six putative transmembrane domains near the N-terminus, followed by an ATP-binding cassette domain. Savary, et al. (supra) also disclosed a partial protein sequence from human similar to the C-terminal 340 amino acids of mouse ABC7 protein. Savary et al. reported that the human ABC7 was widely expressed in cell lines, heart, skeletal muscle, pancreas, lung, liver, and placenta. Human ABC7 expression was not detected in brain.
The discovery of a new human ATP-binding cassette transport protein and the polynucleotides encoding it satisfies a need in the art by providing new compositions which are useful in the diagnosis, prevention and treatment of cancer and neuronal disorders.